Preparation of highly dispersed W/Al2O3 hydrodesulfurization catalysts via a microwave hydrothermal method: Effect of oxalic acid

The role of heterogeneous catalysts in the plasma-catalytic ammonia synthesis

“…43 Most other metal oxides (Table 1Table 1) were also significantly reduced in plasma, in agreement with literature. [44][45][46][47][48][49][50][51][52] The oxides of W, Mo, V, and Mn were only partially reduced because they require a temperature of above at 800 o C in H2 for complete reduction. The Ni, Cu, Fe, Co catalysts likely contained metal sites on their surface while the bulk reduction was limited by diffusion limitations of hydrogen through the oxides.…”

Preparation of highly dispersed W/ZrO2–Al2O3 hydrodesulfurization catalysts at high WO3 loading via a microwave hydrothermal method

“…Because the microwave hydrothermal treatment allows for rapid heating and localized high temperature, and thus accelerates the nucleation and recrystallization of tungstic acid, significantly inhibiting the crystallites growth. In addition, the effective collision rate of tungstic acid can be increased under the microwave hydrothermal environment due to tungstic acid can act as a strong microwave absorber at 2.45 GHz, which promotes the mobility of tungsten species and hence helps to disperse them on support homogeneously and quickly [12,13]. Therefore, the MWH method could produce small nanosized WO 3 on support and hence disperse more WO 3 .…”

“…Compared to the HD method, the MWH method can further improve the dispersion of W and disperse more W onto Al 2 O 3 , while the preparation time can be extremely reduced from 12 h to several minutes [12]. Moreover, the well dispersed W species can be achieved even without oxalic acid [13].…”

“…Recently, a surfactant or oxalic acid-assisted hydrothermal deposition (HD) method was reported to achieve this aim by precipitating WO 3 and dispersing them onto Al 2 O 3 under hydrothermal environment, wherein surfactant or oxalic acid could act as dispersant and additive to prevent WO 3 from aggregation and modify Al 2 O 3 surface [5,10,11]. The latest work is developing a microwave hydrothermal (MWH) method to reduce hydrothermal period and increase preparation efficiency [12,13]. Compared to the HD method, the MWH method can further improve the dispersion of W and disperse more W onto Al 2 O 3 , while the preparation time can be extremely reduced from 12 h to several minutes [12].…”

Supported nanocatalysts: recent developments in microwave synthesis for application in heterogeneous catalysis

“…W/Al 2 O 3 catalyst (identified as MWH-B), prepared by part wise addition of oxalic acid, showed increased HDS activity due to better WO 3 dispersion. 139 Overall analysis suggested that the catalyst prepared by MWH method had superior HDS activity relative to that prepared by IM. Hence the Ti inclusion promised control of the HDA activity over the CoMo/SBA-15 catalyst.…”